The present invention relates to a multi-position switch, in particular for motor vehicles.
More particularly, it relates to a multi-position switch which has an input fixed contact arranged on a switch base and a plurality of output fixed contacts which can be connected with the input fixed contact by one or several contact bridges controlled by ramps and cooperating control parts. The contact bridges are supported on a driver which is turnable or displaceable relative to the switch base under the action of pressure springs which produce the required contact pressure between the contact bridge and the input fixed contact and also between each contact bridge and the fixed contact and which are individually guided. Each contact bridge has an axle which freely rotatable relative to the driver and rolls with a contact roller on the output fixed contacts and directly cooperates through a control part with the control ramp.
A multi-position switch, particularly for a motor vehicle can have an input fixed contact arranged on the switch base and a plurality of output fixed contacts which can be connected with the input fixed contact by one or several contact bridges controlled by ramps and cooperating control parts, with the contact bridges supported on a driver rotatable or displaceable relative to the switch base under the action of pressure springs which produce the required the contact pressure between contact bridges and the input fixed contact, and also between the contact bridges and the fixed contact and guided individually. Here, each contact bridge has an axle which is freely rotatable relative to the driver with a contact roller which rolls on the output fixed contacts. The contact roller is arranged rotatably on the axle of the contact bridge and cooperates directly with a control ramp through a control part.
The present invention is a further development of the prior art as disclosed in the German documents DE 34 14 161 A1, DE 33 15 994 C2 and DE 32 19 853 A1.
It has been recognized that in such multi-position with increasing operation life the contact burning between the contact rollers of the contact bridges and the outwardly located fixed contacts can occur at predetermined permanent points. Therefore the operational safety of such switches can be affected without limiting the remaining regions of the contact parts in their operational ability by a contact burning.
German document DE 34 14 161 A1 shows a multi-position switch, especially for a motor vehicle which has a fixed contact arranged on a switch base and a plurality of output fixed contacts which can be connected with the input fixed contact by one or several contact bridges controlled by ramps and cooperating control parts. The contact bridges are supported on a driver which is turnable and displaceable relative to the switch base under the action of pressure springs which produce the required contact pressure between the contact bridge and the input fixed contact and also between the contact bridge and the fixed contact on the other hand and are guided individually. Each contact bridge has either an axle which is freely rotatable relative to the driver and rolls with a contact roller on the output fixed contacts, or a contact roller which is rotatably arranged on the axle of each contact bridge. Each contact bridge or contact roller directly cooperates with the control ramp through its control part. In these multiple switches the contact rollers are formed themselves as control parts which cooperate with the control paths or ramps.
German patent application DE C 8013 VIIIb/21c filed on Aug. 6, 1953 and published on Oct. 31, 1956 discloses a contact arrangement for switching devices with a contact roller. In this arrangement the contact roller for avoiding the damaging action of switching sparks and light arcs during the contact performs a small rotation and therefore the contact established during the following switching takes place at another location of the roller. The current is turned off and on in this contact arrangement in that a contact block is placed onto the outer surface of the contact roller or lifted from it. The contact surface of the contact block slightly deviates from the rectangular position relative to the movement direction of the contact block, so that the contact pressure does not extend through the center point of the roller. Thereby a torque is applied to the roller and results in a turning of the roller. Such a construction is however not suitable for the use in multi-position switches of the above mentioned type in which the contact of the contact rollers is obtained and interrupted by ramps.
The same is true for a further contact arrangement which is disclosed in the German document DE-GM 16 94 862 and is used for switching and regulating devices with contact rollers. Here the contact rollers are formed not cylindrically but for reducing the contact friction they have a spherical construction. The contact rails or contact paths can be flat and can be provided with a groove shaped depression. The contact rollers are inclined to produce a sliding movement which results first in a self cleaning during the switching process, and also due to the rotation of the contact rollers relative to the contact paths, other contact points are formed. This known contact arrangement is however not suitable for multi-position switches of the above mentioned general type for the reasons specified hereinabove.
U.S. Pat. 2,820,126 discloses a contact roller with a flanged peripheral surface which produces a rubbing friction during rotation of the contact roller about its longitudinal axis by a direct engagement with the contact surface on a fixed contact bench. Since the contact roller with its flanged peripheral surface can however come in contact directly with the outer surface of the fixed contact, the rubbing friction continuously changes because of the unavoidable contact burning at the contact roller. Therefore a controllable turning of the contact roller in each switching step is not possible.
Contact rollers with a contact surface which has an increased friction are disclosed for example in the German document DE-OS 29 09 585. Here the contact rollers are composed at least in the region of their outer cylindrical surface and at least locally, of rubber or other synthetic plastic which is made conductive due to addition of conductive particles (metal dust). The turning or displacing switch provided with such contact rollers has however a high wear resistance and operational safety, especially contact reliability, during selective connection of contact surfaces which are formed as conductor paths and are located relatively close to one another on an isolating material plate.